We propose a clinical and quantitative evaluation of a novel digital subtraction fluoroscopic (DSF) system using two video processors in series for intravenous (IV) angiography). This system is inexpensive and we believe, approaches the minimum requirements for digital subtraction fluoroscopy yet, (1) produces a real-time, continuous subtraction sequence, (2) improves the signal-to-noise ratio by averaging together up to 128 video frames generated at fluoroscopic levels, (3) does not require an interface to the x-ray generator, and (4) can use either a moving or frozen mask image for subtraction. This system has produced high quality subtraction images of peripheral and central arteries of dogs using modest intravenous bolus injections (o.5-1ml/kg) of contrast medium at low injection rates (less than 10 ml/sec). We propose to assess the system's performance quantitatively, particularly its contrast-detail-dose relationship, and to explore methods for improving subtraction imaging, for example by beam filtration. Finally, we hope to determine the clinical utility of the DSF system for diagnosing specific human arterial disease following an IV injection. This assessment will be done by comparing the DSF results to those obtained with serial film arteriography in the same patients. Once validated in this manner, a standardized technique will be applied to other patient subgroups not undergoing selective arteriography which will provide diagnostic information on which patient management can be based. The development of a successful optimized digital radiographic system which has been critically evaluated would be a major contribution to patient care providing images of arteriographic quality without the dangers and expense of catheterization.